package com.leedane.cn.util;

import java.util.HashMap;
import java.util.Map;

/**
 * base64位的加密和解密
 * Created by LeeDane on 2016/4/14.
 */
public class Base64Util{
  /**
    * 将原始数据编码为base64编码
    */
	public static char[] encode(byte[] data){
        char[] out = new char[((data.length + 2) / 3) * 4];

        for (int i = 0, index = 0; i < data.length; i += 3, index += 4){
                boolean quad = false;
                boolean trip = false;
                int val = (0xFF & (int) data[i]);
                val <<= 8;
                if ((i + 1) < data.length){
                        val |= (0xFF & (int) data[i + 1]);
                        trip = true;
                }
                val <<= 8;
                if ((i + 2) < data.length){
                        val |= (0xFF & (int) data[i + 2]);
                        quad = true;
                }
                out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
                val >>= 6;
                out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
                val >>= 6;
                out[index + 1] = alphabet[val & 0x3F];
                val >>= 6;
                out[index + 0] = alphabet[val & 0x3F];
        }
        return out;
    }
    /**
    * 将base64编码的数据解码成原始数据
    */
    public static byte[] decode(char[] data){
      int len = ((data.length + 3) / 4) * 3;
      
      if(data.length > 0 && data[data.length - 1] == '=')
        --len;
      if(data.length > 1 && data[data.length - 2] == '=')
        --len;
      byte[] out = new byte[len];
      int shift = 0;
      int accum = 0;
      int index = 0;
      for(int ix = 0; ix < data.length; ix++){
        int value = codes[data[ix] & 0xFF];
        if(value >= 0){
          accum <<= 6;
          shift += 6;
          accum |= value;
          if(shift >= 8){
            shift -= 8;
            out[index++] = (byte)((accum >> shift) & 0xff);
          }
        }
      }
      if(index != out.length)
        throw new Error("miscalculated data length!");
      return out;
    }

    private static char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();

    private static byte[] codes = new byte[256];
    static {
            for (int i = 0; i < 256; i++)
                    codes[i] = -1;
            for (int i = 'A'; i <= 'Z'; i++)
                    codes[i] = (byte) (i - 'A');
            for (int i = 'a'; i <= 'z'; i++)
                    codes[i] = (byte) (26 + i - 'a');
            for (int i = '0'; i <= '9'; i++)
                    codes[i] = (byte) (52 + i - '0');
            codes['+'] = 62;
            codes['/'] = 63;
    }
}